4. ReSpONSe TIme
15
Some of the typical response times encountered when using
these three types of junctions:
•
Insulated
4.5 seconds
•
Grounded
1.7 seconds
•
Exposed
0.1 seconds
All values are for 6.35 mm outside diameter mineral insulated
cable.
Values listed are based on the average response time of several
minerally insulated cables. The time in seconds indicates time
taken to undergo a change in temperature of 63.2 %.
The tests where performed during a step change from room tem-
perature to boiling water.
Test per ASTM STP 470A (full response is approximated fve time
constants).
As a general rule, it can be stated that the greater the mass of
the junction, the greater the response time and the longer the
service life.
RESPONSE TIME
Diameter
Junction
Time in sec.
0.5 mm
insulated
0.15
0.5 mm
grounded
0.05
1.0 mm
insulated
0.3
1.0 mm
grounded
0.1
3.0 mm
insulated
1.3
3.0 mm
grounded
0.7
4.8 mm
insulated
2.2
4.8 mm
grounded
1.1
6.0 mm
insulated
4.5
6.0 mm
grounded
2.1
6.0 mm
exposed
0.1